Drag bit



E. O. MILLS April 15, 1958 DRAG BIT Filed Feb. 21, 1955 M M .0 m w E Q n M 2 m T w A United States Patent O DRAG BIT Edward 0. Mills, Shawn'ee,'0kla., assignor to Mills Machine Company, Shawnee, kla., a partnership Application February 21, 1955, Serial No. 489,506

4 Claims. (Cl. 255-61) This invention relates to improvements in well drilling bits, and more particularly, but not by way of limitation, to an improved drag bit for use with rotary drilling equipment.

In the drilling of bore holes, it has been found that rotary rock bits are best suited for penetrating hard subsurface formations. A rotary bit, however, will often encounter difiiculties in soft or gummy formations and the cutters will often roll in the sticky formations without penetrating therethrough. As a consequence, it has been found desirable to use a drag bit in many of these formations in order to more efficiently penetrate the strata. In the use of drag bits it has been found that they will sometimes not perform efliciently in sticky, pliable formations because of the difficulty of removing the drill cuttings from the bottom of the bore hole. In the drilling opera-tion it is most important to remove the drill cuttings from the bottom of the bore as soon as they are cut from the formation to prevent the bit from functioning merely to break up the cuttings into finer particles instead of penetrating further into the formation. It will be apparent that the efficiency of the drilling operation drag bit for rotary drilling which assures sufiicient discharge of circulating fluid directly into the drill cuttings to assure rapid removal thereof from the bottom of the bore hole.

It is still another object of this invention to provide an improved drag bit for rotary drilling which will substantially increase the rate of penetration in soft or gummy formations, and thereby reduce drilling costs.

It is a further object of this invention to provide an improved drag bit for rotary drilling which is simple and economical in construction.

Other objects and advantages of the invention willbe evident from the following detailed description, read in conjunction with the accompanying drawings, which illustrate my invention.

In the drawings:

Figure 1 is a side elevational view of a drag bit embodying the invention.

will be greatly impaired by an inadequate removal of the cuttings.

Many present day drag bitsare provided with a plurality of wings having cutter teeth thereon which are substantially horizontally disposed, thus as the bit is rotated, at fiat bottomed bore hole is. produced. It will be apparent that cuttings may be trapped beneath the bit, and may not be readily removed during the drilling operation. Some present day drag bits in use are substantially conical shaped, and have the leading edge thereof centrally disposed so that the cuttings are forced outward and into the path of the outer teeth of the cutter wings, thus hampering the drilling operation.

The present invention contemplates an improved drag bit which facilitates the removal of cuttings from the proximity of the cutting surface of the bit. The novel bit is provided with a plurality of cutter teeth disposed on cutter wings, or segments which provide a substantially inverted conical shaped cutting surface wherein the outer teeth form the leading edge. Thus, as the outer teeth bite into the formation, the cuttings are directed inwardly toward the axial center of the bit. A plurality of longitudinal bores discharge the circulating fluid from the bit and directly into the accumulating cuttings to quickly wash them upwardly away from the bottom of the bore hole. The inverted conical shape of the wings directs the cuttin s inwardly to the smallest diameter portion of the bit, thus facilitating the removal of the cuttings around the wings.

It is, therefore, an important object 'of this invention to provide an improved drag bit for rotary drilling which directs the drill cuttings inwardly toward the central portion of the bit to facilitate the removal of the cuttings from the bot-tom of the bore hole, thereby increasing the cutting efliciency of the bit.

It is another object of this invention to provide a novel Figure 2 is an end view of the novel drag bit taken on line 22 of Figure 1.

Referring to the drawings in detail, reference character 10 indicates generally a substantially cylindrical drag bit body, preferably made of a cast metal and having an upper shank 12 provided with internal threads (not shown) for connection with a drill string (not shown) in a manner well known in the drilling industry. The lower portion of the body 10 is provided with a plurality of outwardly extending substantially radial cutter segments or wings 14. As shown herein, it is preferable to utilize three of the wings 14, but it will be apparent that two, four, or any desired number may be provided. Each radial segment 14 is provided with a plurality of cutter teeth 16 which are disposed in a substantially stair step arrangement at the lower extremity of the wings 14 so-that the innermost teeth 18 are in a higher vertical disposition than the outermost teeth 2t). Thus, the surface of revolution of the cutter teeth 16 is substantially conical, with the vertex thereof disposed at the axial center portion 22 (Fig. 2) of the body 10. An aperture 24 is provided in the body 10 substantially medial between each of the adjacent wing segments 14 and cooperates with an internal longitudinal bore (not shown) which extends downwardly within-the body 10 for a purpose as will hereinafter be set forth.

Each of the teeth 16 is provided with at least one substantially arcuate shaped face 26 (Fig. l) which 'complements an oppositely disposed fiat face 28 to provide a tooth crest 30. It is preferable to provide each tooth crest lit) with a rectangular shaped cutter insert 32, preferably made of tungsten carbide or similar hard metal, which maybe secured to the leading edge thereof in any suitable manner, such as welding, or the like.

Operation The drag bit body 10 is threadedly secured to the lower end of a drilling string (not shown) which is then disposed within a well bore (not shown). The drilling string transmits rotational movement from the surface of the well to the bit 10 disposed at the bottom of the bore hole. As the bit is rotated, the outer teeth 25) will bite into the sub-surface formation and cut portions thereof away. These cuttings will be forced inwardly and upwardly toward the center portion 22 of the body It). In this position, the cuttings are disposed adjacent the smallest diameter of the body 10 and will encounter little resistance therefrom as they move upwardly away from the bottom of the bore hole. Drilling fluid which is usually circulated downwardly through the drill string will enter the longitudinal bore (not shown) within the body 10 and will jettison downwardly through the aper tures 24 directly into the path of the cuttings to quickly wash them away. The cuttings will seek the line of least resistance as they are impinged by the drilling fluid, thus they will move upward between the segments .14 and around the body it] and away from the bottom of the bore hole. In this manner, it is assured that the bit It] will constantly bite into the'formation forfurther penetration, and will not expend unnecessary time grinding up the cuttings.

From the foregoing, it will be apparent that the present invention provides a novel drag bit which utilizes a conical shaped cutting surface to urge the cuttings broken from the formation inwardly to be impinged by a jet action of drilling fiuid which will readily and easily wash the cuttings away from the bottom of the bore hole to substantially preclude interference thereby as .the bit penetrates further into the formation. The one piece bit body hasno free moving parts to become clogged, or the like, by soft. or gummy formations. Further, the hard metal inserts assure a longer useful life ofthe cutter teeth, thereby reducing delay in drilling time by reducing bit replacement. Thus, the novel bit is not only of economical construction, but also reduces drilling cost by increasing the rate of penetration and reducing the operation time.

Changes may be made in the combination and arrangement of parts as heretofore set forth in the specification and shown in the drawings, it being understood that any modification in the precise embodiment of the invention may be made within the scope of the following claims without departing from the spirit of the invention.

I claim:

1. A drag bit for utilization with a drilling string in a rotary drilling operation and comprising a plurality of outwardly extending radial cutting segments, cutter'teeth disposed in stair stepped arrangement on the lower extremity of the radial segments to provide a substantially stair stepped conical surface of revolution having the vertex thereof disposed vertically above the base thereof, :said teeth so constructed and arranged to provide a'plurality of concentric rows of teeth with the outer-most row providing the leading cutting edge for the bit, the innermost teeth being conterminous with each other at the radial center of the hit, each cutter tooth in each row having one arcuate shaped face complementing a substantially straight edge, said straight edge providing a leading cutting edge for each tooth.

2. A drag bit for utilization with a drilling string in rotary drilling of bore holes and comprising a unitary metal body, said body having a plurality of outwardly extending radial wings, a plurality of cutter teeth provided on the lower extremity of the wings in substantially stepped disposition to provide a stair stepped conical surface of revolution having the vertex thereof disposed vertically above thebase thereof, the innermost of said teeth conterminous at the center of the bit, said teeth adapted to penetrate the bottom of the bore hole in a manner to eject cuttings therefrom upwardly and inwardly from the bottom of the bore, and means for circulating fluid into contact with the upwardly eject-2d cuttings for removal from the bore.

3. A drag bit for utilization with a drilling string in rotary drilling of bore holes and comprising a unitary metal body, said drilling string having drilling fluid circulating therethrouglnsaid body comprising a plurality of outwardly extending radial Wings, a plurality of cutter teeth provided on the lower extremity of the wings in substantially stair stepped disposition to provide a-substantially stair stepped conical surface of revolution having the vertex thereof disposed vertically above the thereof, the innermost of said teeth conterminous at the center of the bit to provide a cutting edge throughcut the diameter thereof, said teeth adapted to penetrate the bottom of the bore hole in a manner to eject cuttings therefrom upwardly and inwardly from the bottom of the bore, and aperture means for injecting the drilling fluid into the proximity of the cuttings to facilitate re moval thereof from the bottom of the bore.

4. A drag bit for utilization with a drilling string in rotary drilling of bore holes and comprising a unitary metal body, said drilling string having drilling fluid circulating therethrough, said body comprising a plurality of cutter teeth provided on the lower extremity of the wings in substantially stair stepped disposition throughout the diameter of the-bit to provide a substantially stair stepped conical surface of revolution therefor having the vertex disposed vertically above the base thereof, said teeth adapted to penetrate the bottom of the bore hole in a manner to eject cuttings therefrom upwardly and inwardly-from the bottom of the bore, and aperture means disposed substantially medial between the cutter wings for injecting the drilling fluid into the proximity of the cuttings to'facilitate removalthereof from the bottom of the bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,868,074 Reese July 19, 1932 1,923,488 vHoward et al. Aug. 22, 1933 1,961,390 Ragsdale l'une 5, 1934 2,199,692 Catland May 7, 1940 2,300,805 Pew Nov. 3, 1942 

